Models help set ecosystem service baselines for restoration assessment

Coastal suburban watersheds are under heavy pressure from human activity. This pressure has yielded an extensive effort to protect, mitigate, and restore watershed ecosystem services. Assessment of restoration investments would be greatly improved by a standard approach for estimating change in ecosystem service production combined with a well-defined baseline for assessment of restoration effects. Here we take a model-based approach to both objectives by applying two established ecosystem service models in a representative coastal watershed. This watershed has undergone extensive suburbanization resulting in a loss of ecosystem services, which has resulted in heavy restoration investments. We used models to estimate loss of the ecosystem services; clean air, clean water, stable climate, and water storage resulting from suburbanization. We then applied these model-based estimates as a baseline for assessment of restoration focusing on the appropriate restoration scale and considering downstream watershed impacts. The results suggest that losses of ecosystem services, such as flood water storage, from suburbanization have been extensive since 2001, but a comparison of restoration value suggests that restoration has been effective in recouping ecosystem services in some but not all local regions suggesting there are trade-offs to be made in these efforts. These benefits were most evident for the services of clean water and water storage. Models can inform decisions by clarifying what has been lost and estimating what can be regained through restoration action. The former sets a baseline for the latter and allows for a functional equivalency approach to assessment.